Skin is the external covering of a body. It constitutes a barrier against environmental stresses. Skin is apt to suffer from injury caused by a mechanical stress (e.g., knife traumas), physical stress (e.g., sunburns or cold injury) or chemical stress (e.g., strong acids or alkalis). It is unavoidable in modem society for people to suffer skin injury (such as incised wounds, scalds or sunburns).
Skin injury caused by thermal, chemical or even electrical contact primarily results in burn wound edema and loss of intravascular fluid volume due to increased vascular permeability. Occasionally, subsequent systemic syndromes, such as hypovolemic shock or infection, may occur which are greater threats to life than the primary effects.
In spontaneous healing, dead tissue sloughs off as new epithelium begins to cover the injured area. With superficial bums (e.g., sunburns), regeneration usually occurs rapidly from uninjured epidermal elements, follicles and glands. There is non-significant or little scaring only if no infection occurs.
In the case of destruction of the epidermis or even much of the dermis, reepithelialization starts from the edges of the wound, the scattered remains of integument, or the remaining dermal appendages. This procedure is relatively slow. Excessive granulation tissue forms before being covered by epithelium. To this end, the wounds generally contract and develop to disfiguring or disabling scars unless proper and prompt treatments are employed.
The external drugs for healing wounds in humans are well known in the art. Those drugs include anti-bacterial agents, such as Povidone iodine or silver sulfadiazine; antibiotics, such as neomycin; and compound preparations with corticosteroids (e.g., hydrocortisone). However, the customary anti-bacterial agents are both irritating and toxic and are solely capable of preventing the wound from becoming infected. This expected effect of the application of antibiotics may not be achieved in view of the resistant factors prevailing in modem germs. In some cases the topical application of antibiotics (such as neomycin) may result in contact dermatitis in patients. Corticosteroids are known as the most effective anti-inflammatory agents. However, they are found to make some complications (such as some fungal infections) worse. In case of the topical application of corticosteroids with an occlusive dressing covering the treated area, miliaria, atrophic striae or bacterial infections may follow the occlusive therapy. Pituitary or cortisol suppression was found in the children subject to prolonged occlusive treatment of large areas.
Most importantly, traditional external preparations comprising the above-mentioned agent(s) are incapable to exhibit the dual functions of both promoting wound healing and preventing the formation of scars or granulation tissues. The disfiguring scars or granulation tissues usually cause secondary or even permanent adverse impacts to the patients who have recovered from traumas, especially if they are significant and visible, e.g., on the head or face.
Therefore, there is still a need in the art to develop a novel pharmaceutical composition which is both effective in enhancing wound healing and capable of preventing formation of scars or granulation tissues by helping regenerate to normal tenderness and appearance.